Isometric exercises strengthen muscles without moving the muscles. Isometric exercises tense muscles but do not change the angle of the joint or cause the muscle to lengthen or contract like normal exercises do. These exercises usually consist of "holding" a certain position in which some muscle or muscles are tensed. A prime example of such an exercise is the plank. A.
contracting muscle fibers
B.
changing muscle length
C.
burning calories
D.
conscious effort